High-density, crack-free metallic parts

ABSTRACT

In various embodiments, three-dimensional layered metallic parts are substantially free of gaps between successive layers, are substantially free of cracks, and have densities no less than 97% of the theoretical density of the metallic material.

RELATED APPLICATION

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 62/302,847, filed Mar. 3, 2016, the entiredisclosure of which is hereby incorporated herein by reference.

TECHNICAL FIELD

In various embodiments, the present invention relates to high-density,crack-free metallic parts fabricated via additive manufacturingtechniques.

BACKGROUND

Additive manufacturing, or three-dimensional (3D) printing, is a widelyutilized technique for rapid manufacturing and rapid prototyping. Ingeneral, additive manufacturing entails the layer-by-layer deposition ofmaterial by computer control to form a three-dimensional object. Mostadditive manufacturing techniques to date have utilized polymeric orplastic materials as raw materials, as such materials are easily handledand melt at low temperatures. Since additive manufacturing involves themelting of only small amounts of material at a time, the process has thepotential to be a useful technique for the fabrication of large, complexstructures composed of metal as well. Unfortunately, additivemanufacturing of metallic materials is not without its challenges. Whenfabricating a three-dimensional part with a metallic precursor materialvia additive manufacturing, the melting of the precursor material mayresult in sparking, blistering, and splattering (i.e., ejection of smallpieces of the precursor material itself). In addition, even if thethree-dimensional part is successfully fabricated utilizing conventionalprecursor materials, the part may exhibit excessive porosity, cracking,material splatter, and insufficient density and machinability.

In view of the foregoing, there is a need for improved precursormaterials for the additive manufacturing of metallic parts.

SUMMARY

In accordance with various embodiments of the present invention, wiresfor use as feedstock for additive manufacturing processes are fabricatedsuch that the amounts of gaseous and/or volatile impurities therein arereduced or minimized. As utilized herein, the term “volatile elements”refers to elements having boiling points lower than the melting point ofthe nominal, majority wire material. For example, the concentrations ofelements such as oxygen (O), sodium (Na), magnesium (Mg), phosphorus(P), sulfur (S), potassium (K), calcium (Ca), and antimony (Sb) may bekept below a concentration of 20 ppm, below a concentration of 10 ppm,below a concentration of 5 ppm, below a concentration of 3 ppm, below aconcentration of 2 ppm, or even below a concentration of 1 ppm (allconcentrations herein are by weight unless otherwise indicated), and oneor more, or even all, of these elements may be volatile elements invarious embodiments of the present invention. The precursor wire itselfmay include, consist essentially of, or consist of one or morerefractory metals, e.g., niobium (Nb), tantalum (Ta), rhenium (Re),tungsten (W), and/or molybdenum (Mo). The wire may be utilized in anadditive manufacturing process to form a three-dimensional part, e.g., arefractory crucible.

In various embodiments of the invention, the precursor wire isfabricated, at least partially, via arc melting in a vacuum or asubstantially inert ambient. The arc-melting process advantageouslyminimizes or reduces the concentration of volatile impurities within thewire, thereby enabling successful additive manufacturing processesutilizing the wire. The resulting wire is utilized in an additivemanufacturing process to form a three-dimensional part composed, atleast partially, of the precursor material. In exemplary embodiments,the wire is fed toward a movable platform, and the tip of the wire ismelted by, e.g., an electron beam or a laser. The platform (and/or thewire) moves such that the molten wire traces out the pattern of asubstantially two-dimensional slice of the final part; in this manner,the final part is fabricated in layer-by-layer fashion via melting andrapid solidification of the wire. In such additive manufacturingprocesses, the wire is successfully melted during formation of thethree-dimensional part with minimal (if any) sparking, blistering,and/or splattering. In addition, the finished part exhibits a highdensity (e.g., greater than 96%, greater than 97%, greater than 98%, oreven greater than 99% of the theoretical density) without the porosityor cracking that may accompany use of conventional powder metallurgyfeedstock materials, particularly those for refractory metals.

Wire in accordance with embodiments of the invention may also beutilized in a variety of different wire-fed welding applications (e.g.,MIG welding, welding repair) in which an electric arc is struck betweenthe wire and a workpiece, causing part of the wire to fuse with theworkpiece.

In an aspect, embodiments of the invention feature a method offabricating a three-dimensional part that includes, consists essentiallyof, or consists of molybdenum. In a step (a), powder is compacted toform a feed electrode. The powder includes, consists essentially of, orconsists of molybdenum. In a step (b), the feed electrode is arc-meltedin a processing ambient including, consisting essentially of, orconsisting of a vacuum or one or more inert gases, thereby forming abillet. In a step (c), the billet is mechanically deformed into wirehaving a diameter (or other dimension, e.g., width) less than a diameter(or other dimension, e.g., width) of the billet. In a step (d), a tip ofthe wire is translated relative to a platform (i.e., all or a portion ofthe wire is translated, the platform is translated, or both). In a step(e), while the tip of the wire is being translated, the tip of the wireis melted with an energy source to form a molten bead, whereby the beadcools to form at least a portion of a layer of a three-dimensional part.In a step (f), steps (d) and (e) are repeated one or more times toproduce the three-dimensional part (or at least a portion thereof). Thethree-dimensional part includes, consists essentially of, or consists ofmolybdenum.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. A concentration within the wire ofsodium, calcium, antimony, magnesium, phosphorous, and/or potassium maybe less than 5 ppm by weight, less than 4 ppm by weight, less than 3 ppmby weight, less than 2 ppm by weight, or less than 1 ppm by weight. Aconcentration within the wire of sodium, calcium, antimony, magnesium,phosphorous, and/or potassium may be no less than 0.001 ppm by weight,no less than 0.005 ppm by weight, no less than 0.01 ppm by weight, noless than 0.05 ppm by weight, no less than 0.1 ppm by weight, or no lessthan 0.5 ppm by weight. A concentration of oxygen within the wire may beless than 25 ppm by weight, less than 22 ppm by weight, less than 20 ppmby weight, less than 19 ppm by weight, less than 18 ppm by weight, lessthan 15 ppm by weight, or less than 10 ppm by weight. A concentration ofoxygen within the wire may be no less than 0.001 ppm by weight, no lessthan 0.005 ppm by weight, no less than 0.01 ppm by weight, no less than0.05 ppm by weight, no less than 0.1 ppm by weight, no less than 0.5 ppmby weight, no less than 1 ppm by weight, or no less than 2 ppm byweight. The density of at least a portion of the three-dimensional partmay be greater than 97% of a theoretical density of molybdenum, greaterthan 98% of a theoretical density of molybdenum, greater than 99% of atheoretical density of molybdenum, or greater than 99.5% of atheoretical density of molybdenum. The density of at least a portion ofthe three-dimensional part may be no greater than 100% of a theoreticaldensity of molybdenum, no greater than 99.9% of a theoretical density ofmolybdenum, or no greater than 99.8% of a theoretical density ofmolybdenum. Step (c) may include, consist essentially of, or consist ofdrawing, rolling, swaging, extruding, and/or pilgering. Step (a) mayinclude sintering the compacted powder at a temperature greater than900° C., greater than 950° C., greater than 1000° C., greater than 1100°C., or greater than 1200° C. Step (a) may include sintering thecompacted powder at a temperature less than 2500° C. In step (e), theenergy source may include, consist essentially of, or consist of anelectron beam and/or a laser beam. Prior to step (a), the powder may beprovided by a process including, consisting essentially of, orconsisting of plasma densification and/or plasma atomization. Prior tostep (a), the powder may be provided by a process including, consistingessentially of, or consisting of (i) hydrogenating metal to form a metalhydride, (ii) mechanically grinding the metal hydride into a pluralityof particles, and (iii) dehydrogenating the metal hydride particles.Embodiments of the invention include three-dimensional objects or partsfabricated according to any of the above methods.

In another aspect, embodiments of the invention feature a method offabricating a three-dimensional part utilizing wire. The part includes,consists essentially of, or consists of molybdenum. The wire is producedby a process including, consisting essentially of, or consisting of (i)compacting powder to form a feed electrode, the powder including,consisting essentially of, or consisting of molybdenum, (ii) arc-meltingthe feed electrode in a processing ambient including, consistingessentially of, or consisting of a vacuum or one or more inert gases,thereby forming a billet, and (iii) mechanically deforming the billetinto wire having a diameter (or other dimension, e.g., width) less thana diameter (or other dimension, e.g., width) of the billet. In a step(a), a tip of the wire is translated relative to a platform (i.e., allor a portion of the wire is translated, the platform is translated, orboth). In a step (b), while the tip of the wire is being translated, thetip of the wire is melted with an energy source to form a molten bead,whereby the bead cools to form at least a portion of a layer of athree-dimensional part. In a step (c), steps (a) and (b) are repeatedone or more times to produce at least a portion of the three-dimensionalpart. The three-dimensional part includes, consists essentially of, orconsists of molybdenum.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. A concentration within the wire ofsodium, calcium, antimony, magnesium, phosphorous, and/or potassium maybe less than 5 ppm by weight, less than 4 ppm by weight, less than 3 ppmby weight, less than 2 ppm by weight, or less than 1 ppm by weight. Aconcentration within the wire of sodium, calcium, antimony, magnesium,phosphorous, and/or potassium may be no less than 0.001 ppm by weight,no less than 0.005 ppm by weight, no less than 0.01 ppm by weight, noless than 0.05 ppm by weight, no less than 0.1 ppm by weight, or no lessthan 0.5 ppm by weight. A concentration of oxygen within the wire may beless than 25 ppm by weight, less than 22 ppm by weight, less than 20 ppmby weight, less than 19 ppm by weight, less than 18 ppm by weight, lessthan 15 ppm by weight, or less than 10 ppm by weight. A concentration ofoxygen within the wire may be no less than 0.001 ppm by weight, no lessthan 0.005 ppm by weight, no less than 0.01 ppm by weight, no less than0.05 ppm by weight, no less than 0.1 ppm by weight, no less than 0.5 ppmby weight, no less than 1 ppm by weight, or no less than 2 ppm byweight. The density of at least a portion of the three-dimensional partmay be greater than 97% of a theoretical density of molybdenum, greaterthan 98% of a theoretical density of molybdenum, greater than 99% of atheoretical density of molybdenum, or greater than 99.5% of atheoretical density of molybdenum. The density of at least a portion ofthe three-dimensional part may be no greater than 100% of a theoreticaldensity of molybdenum, no greater than 99.9% of a theoretical density ofmolybdenum, or no greater than 99.8% of a theoretical density ofmolybdenum. Mechanically deforming the billet into wire may include,consist essentially of, or consist of drawing, rolling, swaging,extruding, and/or pilgering. The process of producing the wire mayinclude sintering the compacted powder at a temperature greater than900° C., greater than 950° C., greater than 1000° C., greater than 1100°C., or greater than 1200° C. The process of producing the wire mayinclude sintering the compacted powder at a temperature less than 2500°C. In step (b), the energy source may include, consist essentially of,or consist of an electron beam and/or a laser beam. The process ofproducing the wire may include providing the powder by a processincluding, consisting essentially of, or consisting of plasmadensification and/or plasma atomization. The process of producing thewire may include providing the powder by a process including, consistingessentially of, or consisting of (i) hydrogenating metal to form a metalhydride, (ii) mechanically grinding the metal hydride into a pluralityof particles, and (iii) dehydrogenating the metal hydride particles.Embodiments of the invention include three-dimensional objects or partsfabricated according to any of the above methods.

In yet another aspect, embodiments of the invention feature a method offabricating a three-dimensional part that includes, consists essentiallyof, or consists of molybdenum. In a step (a), a wire including,consisting essentially of, or consisting of arc-melted molybdenum isprovided. In a step (b), a tip of the wire is translated relative to aplatform (i.e., all or a portion of the wire is translated, the platformis translated, or both). In a step (c), while the tip of the wire isbeing translated, the tip of the wire is melted with an energy source toform a molten bead, whereby the bead cools to form at least a portion ofa layer of a three-dimensional part. In a step (d), steps (b) and (c)are repeated one or more times to produce at least a portion of thethree-dimensional part. The three-dimensional part includes, consistsessentially of, or consists of molybdenum.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. A concentration within the wire ofsodium, calcium, antimony, magnesium, phosphorous, and/or potassium maybe less than 5 ppm by weight, less than 4 ppm by weight, less than 3 ppmby weight, less than 2 ppm by weight, or less than 1 ppm by weight. Aconcentration within the wire of sodium, calcium, antimony, magnesium,phosphorous, and/or potassium may be no less than 0.001 ppm by weight,no less than 0.005 ppm by weight, no less than 0.01 ppm by weight, noless than 0.05 ppm by weight, no less than 0.1 ppm by weight, or no lessthan 0.5 ppm by weight. A concentration of oxygen within the wire may beless than 25 ppm by weight, less than 22 ppm by weight, less than 20 ppmby weight, less than 19 ppm by weight, less than 18 ppm by weight, lessthan 15 ppm by weight, or less than 10 ppm by weight. A concentration ofoxygen within the wire may be no less than 0.001 ppm by weight, no lessthan 0.005 ppm by weight, no less than 0.01 ppm by weight, no less than0.05 ppm by weight, no less than 0.1 ppm by weight, no less than 0.5 ppmby weight, no less than 1 ppm by weight, or no less than 2 ppm byweight. The density of at least a portion of the three-dimensional partmay be greater than 97% of a theoretical density of molybdenum, greaterthan 98% of a theoretical density of molybdenum, greater than 99% of atheoretical density of molybdenum, or greater than 99.5% of atheoretical density of molybdenum. The density of at least a portion ofthe three-dimensional part may be no greater than 100% of a theoreticaldensity of molybdenum, no greater than 99.9% of a theoretical density ofmolybdenum, or no greater than 99.8% of a theoretical density ofmolybdenum. In step (c), the energy source may include, consistessentially of, or consist of an electron beam and/or a laser beam. Theprocess of producing the wire may include, consist essentially of, orconsist of (i) compacting powder to form a feed electrode, the powderincluding, consisting essentially of, or consisting of molybdenum, (ii)arc-melting the feed electrode in a processing ambient including,consisting essentially of, or consisting of a vacuum or one or moreinert gases, thereby forming a billet, and (iii) mechanically deformingthe billet into wire having a diameter (or other dimension, e.g., width)less than a diameter (or other dimension, e.g., width) of the billet.Embodiments of the invention include three-dimensional objects or partsfabricated according to any of the above methods.

In another aspect, embodiments of the invention feature athree-dimensional part manufactured by additive manufacturing using afeedstock material that includes, consists essentially of, or consistsof molybdenum. The part includes, consists essentially of, or consistsof a plurality of layers. Each layer includes, consists essentially of,or consists of solidified molybdenum. The part is substantially free ofgaps between successive layers and/or substantially free of gaps withinone or more of the layers. The part is substantially free of cracks. Thedensity of at least a portion of the three-dimensional part may begreater than 97% of a theoretical density of molybdenum, greater than98% of a theoretical density of molybdenum, greater than 99% of atheoretical density of molybdenum, or greater than 99.5% of atheoretical density of molybdenum. The density of at least a portion ofthe three-dimensional part may be no greater than 100% of a theoreticaldensity of molybdenum, no greater than 99.9% of a theoretical density ofmolybdenum, or no greater than 99.8% of a theoretical density ofmolybdenum. A concentration within the part of sodium, calcium,antimony, magnesium, phosphorous, and/or potassium may be less than 5ppm by weight, less than 4 ppm by weight, less than 3 ppm by weight,less than 2 ppm by weight, or less than 1 ppm by weight. A concentrationwithin the part of sodium, calcium, antimony, magnesium, phosphorous,and/or potassium may be no less than 0.001 ppm by weight, no less than0.005 ppm by weight, no less than 0.01 ppm by weight, no less than 0.05ppm by weight, no less than 0.1 ppm by weight, or no less than 0.5 ppmby weight.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. A concentration within the part ofeach of sodium, calcium, antimony, magnesium, phosphorous, and potassiummay be less than 5 ppm by weight, less than 4 ppm by weight, less than 3ppm by weight, less than 2 ppm by weight, or less than 1 ppm by weight.A concentration within the part of each of sodium, calcium, antimony,magnesium, phosphorous, and potassium may be no less than 0.001 ppm byweight, no less than 0.005 ppm by weight, no less than 0.01 ppm byweight, no less than 0.05 ppm by weight, no less than 0.1 ppm by weight,or no less than 0.5 ppm by weight. A concentration of oxygen within thepart may be less than 5 ppm by weight, less than 4 ppm by weight, lessthan 3 ppm by weight, less than 2 ppm by weight, or less than 1 ppm byweight. A concentration of oxygen within the part may be no less than0.001 ppm by weight, no less than 0.005 ppm by weight, no less than 0.01ppm by weight, no less than 0.05 ppm by weight, no less than 0.1 ppm byweight, no less than 0.5 ppm by weight, no less than 1 ppm by weight, orno less than 2 ppm by weight. The feedstock material may include,consist essentially of, or consist of wire. The feedstock material mayinclude, consist essentially of, or consist of arc-melted wire (i.e.,wire fabricated at least in part by arc melting). The feedstock materialmay include, consist essentially of, or consist of wire fabricated by aprocess that includes, consists essentially of, or consists of (i)compacting powder to form a feed electrode, the powder including,consisting essentially of, or consisting of molybdenum, (ii) arc-meltingthe feed electrode in a processing ambient including, consistingessentially of, or consisting of a vacuum or one or more inert gases,thereby forming a billet, and (iii) mechanically deforming the billetinto wire having a diameter less than a diameter of the billet.

In an aspect, embodiments of the invention feature method of fabricatinga three-dimensional part that includes, consists essentially of, orconsists of a metallic material. In a step (a), powder is compacted toform a feed electrode. The powder includes, consists essentially of, orconsists of the metallic material. In a step (b), the feed electrode isarc-melted in a processing ambient including, consisting essentially of,or consisting of a vacuum or one or more inert gases, thereby forming abillet. In a step (c), the billet is mechanically deformed into wirehaving a diameter (or other dimension, e.g., width) less than a diameter(or other dimension, e.g., width) of the billet. In a step (d), a tip ofthe wire is translated relative to a platform (i.e., all or a portion ofthe wire is translated, the platform is translated, or both). In a step(e), while the tip of the wire is being translated, the tip of the wireis melted with an energy source to form a molten bead, whereby the beadcools to form at least a portion of a layer of a three-dimensional part.In a step (f), steps (d) and (e) are repeated one or more times toproduce the three-dimensional part (or at least a portion thereof). Thethree-dimensional part includes, consists essentially of, or consists ofthe metallic material.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The metallic material may include,consist essentially of, or consist of one or more refractory metals. Themetallic material may include, consist essentially of, or consist ofniobium, tantalum, rhenium, tungsten, and/or molybdenum. The metallicmaterial may include, consist essentially of, or consist of niobium,tantalum, rhenium, and/or tungsten. A concentration within the wire ofsodium, calcium, antimony, magnesium, phosphorous, and/or potassium maybe less than 5 ppm by weight, less than 4 ppm by weight, less than 3 ppmby weight, less than 2 ppm by weight, or less than 1 ppm by weight. Aconcentration within the wire of sodium, calcium, antimony, magnesium,phosphorous, and/or potassium may be no less than 0.001 ppm by weight,no less than 0.005 ppm by weight, no less than 0.01 ppm by weight, noless than 0.05 ppm by weight, no less than 0.1 ppm by weight, or no lessthan 0.5 ppm by weight. A concentration of oxygen within the wire may beless than 25 ppm by weight, less than 22 ppm by weight, less than 20 ppmby weight, less than 19 ppm by weight, less than 18 ppm by weight, lessthan 15 ppm by weight, or less than 10 ppm by weight. A concentration ofoxygen within the wire may be no less than 0.001 ppm by weight, no lessthan 0.005 ppm by weight, no less than 0.01 ppm by weight, no less than0.05 ppm by weight, no less than 0.1 ppm by weight, no less than 0.5 ppmby weight, no less than 1 ppm by weight, or no less than 2 ppm byweight. The density of at least a portion of the three-dimensional partmay be greater than 97% of a theoretical density of the metallicmaterial, greater than 98% of a theoretical density of the metallicmaterial, greater than 99% of a theoretical density of the metallicmaterial, or greater than 99.5% of a theoretical density of the metallicmaterial. The density of at least a portion of the three-dimensionalpart may be no greater than 100% of a theoretical density of themetallic material, no greater than 99.9% of a theoretical density of themetallic material, or no greater than 99.8% of a theoretical density ofthe metallic material. Step (c) may include, consist essentially of, orconsist of drawing, rolling, swaging, extruding, and/or pilgering. Step(a) may include sintering the compacted powder at a temperature greaterthan 900° C., greater than 950° C., greater than 1000° C., greater than1100° C., or greater than 1200° C. Step (a) may include sintering thecompacted powder at a temperature less than 3500° C., less than 3000°C., or less than 2500° C. In step (e), the energy source may include,consist essentially of, or consist of an electron beam and/or a laserbeam. Prior to step (a), the powder may be provided by a processincluding, consisting essentially of, or consisting of plasmadensification and/or plasma atomization. Prior to step (a), the powdermay be provided by a process including, consisting essentially of, orconsisting of (i) hydrogenating metal to form a metal hydride, (ii)mechanically grinding the metal hydride into a plurality of particles,and (iii) dehydrogenating the metal hydride particles. Embodiments ofthe invention include three-dimensional objects or parts fabricatedaccording to any of the above methods.

In another aspect, embodiments of the invention feature a method offabricating a three-dimensional part utilizing wire. The part includes,consists essentially of, or consists of a metallic material. The wire isproduced by a process including, consisting essentially of, orconsisting of (i) compacting powder to form a feed electrode, the powderincluding, consisting essentially of, or consisting of the metallicmaterial, (ii) arc-melting the feed electrode in a processing ambientincluding, consisting essentially of, or consisting of a vacuum or oneor more inert gases, thereby forming a billet, and (iii) mechanicallydeforming the billet into wire having a diameter (or other dimension,e.g., width) less than a diameter (or other dimension, e.g., width) ofthe billet. In a step (a), a tip of the wire is translated relative to aplatform (i.e., all or a portion of the wire is translated, the platformis translated, or both). In a step (b), while the tip of the wire isbeing translated, the tip of the wire is melted with an energy source toform a molten bead, whereby the bead cools to form at least a portion ofa layer of a three-dimensional part. In a step (c), steps (a) and (b)are repeated one or more times to produce at least a portion of thethree-dimensional part. The three-dimensional part includes, consistsessentially of, or consists of the metallic material.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The metallic material may include,consist essentially of, or consist of one or more refractory metals. Themetallic material may include, consist essentially of, or consist ofniobium, tantalum, rhenium, tungsten, and/or molybdenum. The metallicmaterial may include, consist essentially of, or consist of niobium,tantalum, rhenium, and/or tungsten. A concentration within the wire ofsodium, calcium, antimony, magnesium, phosphorous, and/or potassium maybe less than 5 ppm by weight, less than 4 ppm by weight, less than 3 ppmby weight, less than 2 ppm by weight, or less than 1 ppm by weight. Aconcentration within the wire of sodium, calcium, antimony, magnesium,phosphorous, and/or potassium may be no less than 0.001 ppm by weight,no less than 0.005 ppm by weight, no less than 0.01 ppm by weight, noless than 0.05 ppm by weight, no less than 0.1 ppm by weight, or no lessthan 0.5 ppm by weight. A concentration of oxygen within the wire may beless than 25 ppm by weight, less than 22 ppm by weight, less than 20 ppmby weight, less than 19 ppm by weight, less than 18 ppm by weight, lessthan 15 ppm by weight, or less than 10 ppm by weight. A concentration ofoxygen within the wire may be no less than 0.001 ppm by weight, no lessthan 0.005 ppm by weight, no less than 0.01 ppm by weight, no less than0.05 ppm by weight, no less than 0.1 ppm by weight, no less than 0.5 ppmby weight, no less than 1 ppm by weight, or no less than 2 ppm byweight. The density of at least a portion of the three-dimensional partmay be greater than 97% of a theoretical density of the metallicmaterial, greater than 98% of a theoretical density of the metallicmaterial, greater than 99% of a theoretical density of the metallicmaterial, or greater than 99.5% of a theoretical density of the metallicmaterial. The density of at least a portion of the three-dimensionalpart may be no greater than 100% of a theoretical density of themetallic material, no greater than 99.9% of a theoretical density of themetallic material, or no greater than 99.8% of a theoretical density ofthe metallic material. Mechanically deforming the billet into wire mayinclude, consist essentially of, or consist of drawing, rolling,swaging, extruding, and/or pilgering. The process of producing the wiremay include sintering the compacted powder at a temperature greater than900° C., greater than 950° C., greater than 1000° C., greater than 1100°C., or greater than 1200° C. The process of producing the wire mayinclude sintering the compacted powder at a temperature less than 3500°C., less than 3000° C., or less than 2500° C. In step (b), the energysource may include, consist essentially of, or consist of an electronbeam and/or a laser beam. The process of producing the wire may includeproviding the powder by a process including, consisting essentially of,or consisting of plasma densification and/or plasma atomization. Theprocess of producing the wire may include providing the powder by aprocess including, consisting essentially of, or consisting of (i)hydrogenating metal to form a metal hydride, (ii) mechanically grindingthe metal hydride into a plurality of particles, and (iii)dehydrogenating the metal hydride particles. Embodiments of theinvention include three-dimensional objects or parts fabricatedaccording to any of the above methods.

In yet another aspect, embodiments of the invention feature a method offabricating a three-dimensional part that includes, consists essentiallyof, or consists of a metallic material. In a step (a), a wire including,consisting essentially of, or consisting of arc-melted metallic materialis provided. In a step (b), a tip of the wire is translated relative toa platform (i.e., all or a portion of the wire is translated, theplatform is translated, or both). In a step (c), while the tip of thewire is being translated, the tip of the wire is melted with an energysource to form a molten bead, whereby the bead cools to form at least aportion of a layer of a three-dimensional part. In a step (d), steps (b)and (c) are repeated one or more times to produce at least a portion ofthe three-dimensional part. The three-dimensional part includes,consists essentially of, or consists of the metallic material.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The metallic material may include,consist essentially of, or consist of one or more refractory metals. Themetallic material may include, consist essentially of, or consist ofniobium, tantalum, rhenium, tungsten, and/or molybdenum. The metallicmaterial may include, consist essentially of, or consist of niobium,tantalum, rhenium, and/or tungsten. A concentration within the wire ofsodium, calcium, antimony, magnesium, phosphorous, and/or potassium maybe less than 5 ppm by weight, less than 4 ppm by weight, less than 3 ppmby weight, less than 2 ppm by weight, or less than 1 ppm by weight. Aconcentration within the wire of sodium, calcium, antimony, magnesium,phosphorous, and/or potassium may be no less than 0.001 ppm by weight,no less than 0.005 ppm by weight, no less than 0.01 ppm by weight, noless than 0.05 ppm by weight, no less than 0.1 ppm by weight, or no lessthan 0.5 ppm by weight. A concentration of oxygen within the wire may beless than 25 ppm by weight, less than 22 ppm by weight, less than 20 ppmby weight, less than 19 ppm by weight, less than 18 ppm by weight, lessthan 15 ppm by weight, or less than 10 ppm by weight. A concentration ofoxygen within the wire may be no less than 0.001 ppm by weight, no lessthan 0.005 ppm by weight, no less than 0.01 ppm by weight, no less than0.05 ppm by weight, no less than 0.1 ppm by weight, no less than 0.5 ppmby weight, no less than 1 ppm by weight, or no less than 2 ppm byweight. The density of at least a portion of the three-dimensional partmay be greater than 97% of a theoretical density of the metallicmaterial, greater than 98% of a theoretical density of the metallicmaterial, greater than 99% of a theoretical density of the metallicmaterial, or greater than 99.5% of a theoretical density of the metallicmaterial. The density of at least a portion of the three-dimensionalpart may be no greater than 100% of a theoretical density of themetallic material, no greater than 99.9% of a theoretical density of themetallic material, or no greater than 99.8% of a theoretical density ofthe metallic material. In step (c), the energy source may include,consist essentially of, or consist of an electron beam and/or a laserbeam. The process of producing the wire may include, consist essentiallyof, or consist of (i) compacting powder to form a feed electrode, thepowder including, consisting essentially of, or consisting of themetallic material, (ii) arc-melting the feed electrode in a processingambient including, consisting essentially of, or consisting of a vacuumor one or more inert gases, thereby forming a billet, and (iii)mechanically deforming the billet into wire having a diameter (or otherdimension, e.g., width) less than a diameter (or other dimension, e.g.,width) of the billet. Embodiments of the invention includethree-dimensional objects or parts fabricated according to any of theabove methods.

In another aspect, embodiments of the invention feature athree-dimensional part manufactured by additive manufacturing using afeedstock material that includes, consists essentially of, or consistsof a metallic material. The part includes, consists essentially of, orconsists of a plurality of layers. Each layer includes, consistsessentially of, or consists of solidified metallic material. The part issubstantially free of gaps between successive layers and/orsubstantially free of gaps within one or more of the layers. The part issubstantially free of cracks. The density of at least a portion of thethree-dimensional part may be greater than 97% of a theoretical densityof the metallic material, greater than 98% of a theoretical density ofthe metallic material, greater than 99% of a theoretical density of themetallic material, or greater than 99.5% of a theoretical density of themetallic material. The density of at least a portion of thethree-dimensional part may be no greater than 100% of a theoreticaldensity of the metallic material, no greater than 99.9% of a theoreticaldensity of the metallic material, or no greater than 99.8% of atheoretical density of the metallic material. A concentration within thepart of sodium, calcium, antimony, magnesium, phosphorous, and/orpotassium may be less than 5 ppm by weight, less than 4 ppm by weight,less than 3 ppm by weight, less than 2 ppm by weight, or less than 1 ppmby weight. A concentration within the part of sodium, calcium, antimony,magnesium, phosphorous, and/or potassium may be no less than 0.001 ppmby weight, no less than 0.005 ppm by weight, no less than 0.01 ppm byweight, no less than 0.05 ppm by weight, no less than 0.1 ppm by weight,or no less than 0.5 ppm by weight.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The metallic material may include,consist essentially of, or consist of one or more refractory metals. Themetallic material may include, consist essentially of, or consist ofniobium, tantalum, rhenium, tungsten, and/or molybdenum. The metallicmaterial may include, consist essentially of, or consist of niobium,tantalum, rhenium, and/or tungsten. A concentration within the part ofeach of sodium, calcium, antimony, magnesium, phosphorous, and potassiummay be less than 5 ppm by weight, less than 4 ppm by weight, less than 3ppm by weight, less than 2 ppm by weight, or less than 1 ppm by weight.A concentration within the part of each of sodium, calcium, antimony,magnesium, phosphorous, and potassium may be no less than 0.001 ppm byweight, no less than 0.005 ppm by weight, no less than 0.01 ppm byweight, no less than 0.05 ppm by weight, no less than 0.1 ppm by weight,or no less than 0.5 ppm by weight. A concentration of oxygen within thepart may be less than 5 ppm by weight, less than 4 ppm by weight, lessthan 3 ppm by weight, less than 2 ppm by weight, or less than 1 ppm byweight. A concentration of oxygen within the part may be no less than0.001 ppm by weight, no less than 0.005 ppm by weight, no less than 0.01ppm by weight, no less than 0.05 ppm by weight, no less than 0.1 ppm byweight, no less than 0.5 ppm by weight, no less than 1 ppm by weight, orno less than 2 ppm by weight. The feedstock material may include,consist essentially of, or consist of wire. The feedstock material mayinclude, consist essentially of, or consist of arc-melted wire (i.e.,wire fabricated at least in part by arc melting). The feedstock materialmay include, consist essentially of, or consist of wire fabricated by aprocess that includes, consists essentially of, or consists of (i)compacting powder to form a feed electrode, the powder including,consisting essentially of, or consisting of the metallic material, (ii)arc-melting the feed electrode in a processing ambient including,consisting essentially of, or consisting of a vacuum or one or moreinert gases, thereby forming a billet, and (iii) mechanically deformingthe billet into wire having a diameter less than a diameter of thebillet.

These and other objects, along with advantages and features of thepresent invention herein disclosed, will become more apparent throughreference to the following description, the accompanying drawings, andthe claims. Furthermore, it is to be understood that the features of thevarious embodiments described herein are not mutually exclusive and mayexist in various combinations and permutations. As used herein, theterms “approximately” and “substantially” mean±10%, and in someembodiments, ±5%. The term “consists essentially of” means excludingother materials that contribute to function, unless otherwise definedherein. Nonetheless, such other materials may be present, collectivelyor individually, in trace amounts. For example, a structure consistingessentially of multiple metals will generally include only those metalsand only unintentional impurities (which may be metallic ornon-metallic) that may be detectable via chemical analysis but do notcontribute to function. As used herein, “consisting essentially of atleast one metal” refers to a metal or a mixture of two or more metalsbut not compounds between a metal and a non-metallic element or chemicalspecies such as oxygen, silicon, or nitrogen (e.g., metal nitrides,metal silicides, or metal oxides); such non-metallic elements orchemical species may be present, collectively or individually, in traceamounts, e.g., as impurities.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawings, in which:

FIG. 1 is a schematic cross-sectional view of an arc-melting apparatusutilized to form metallic billets in accordance with various embodimentsof the invention;

FIG. 2 is a schematic view of a wire being fabricated from a metallicrod or billet in accordance with various embodiments of the invention;

FIG. 3 is a schematic of an additive-manufacturing apparatus utilized tofabricate three-dimensional metallic parts in accordance with variousembodiments of the invention;

FIG. 4 is an image of the tip a wire fabricated in accordance withvarious embodiments of the invention during an additive manufacturingprocess;

FIG. 5 is an image of a three-dimensional part fabricated by additivemanufacturing utilizing the wire of FIG. 4;

FIG. 6 is an image of the part of FIG. 5 after machining;

FIG. 7 is an image of the tip of a conventional wire during an additivemanufacturing process; and

FIGS. 8A and 8B are images of a three-dimensional part fabricated byadditive manufacturing utilizing the wire of FIG. 7.

DETAILED DESCRIPTION

In accordance with various embodiments of the invention, a billet of thedesired metallic precursor material is formed via compacting powderincluding, consisting essentially of, or consisting of the precursormaterial (e.g., one or more refractory metals) into a rod or otherthree-dimensional structure. The powders themselves may be initiallyformed utilizing one or more techniques that minimize or substantiallyreduce the amount of oxygen and other volatile elements within thepowders. In this manner, the amount of such volatile species within thewire is minimized or reduced. For example, various powders may be formedand/or treated via a hydride/dehydride process, plasma densification,and/or plasma atomization, and the powders may have low concentrationsof volatile species such as oxygen (e.g., oxygen contents lower than 300ppm, lower than 100 ppm, lower than 50 ppm, or even lower than 30 ppm).As known in the art, hydride/dehydride processes involve theembrittlement of a metal via hydrogen introduction (thereby forming ahydride phase), followed by mechanical grinding (e.g., ball milling) anddehydrogenation (e.g., heating in a vacuum). Various powders or powderprecursors may even be combined with one or more materials (e.g.,metals) having a higher affinity for oxygen (e.g., calcium, magnesium,etc.), deoxidized at high temperature, and then separated from thehigh-oxygen-affinity material via, e.g., chemical leaching, as detailedin U.S. Pat. No. 6,261,337, filed on Aug. 19, 1999 (the '337 patent),the entire disclosure of which is incorporated by reference herein. Asdescribed in U.S. patent application Ser. No. 15/416,253, filed on Jan.27, 2017, the entire disclosure of which is incorporated by referenceherein, in a plasma densification process, metal particulates are fedinto a plasma jet or plasma torch, at least partially melted thereby,and upon cooling tend to have a substantially spherical morphology. Theplasma densification process may also reduce the concentrations ofvolatile elements within the metal powder.

The compacted-powder rod may then be sintered to form a feed electrodefor an arc-melting process. For example, the rod may be sintered at atemperature ranging from approximately 1800° C. to approximately 2200°C. As illustrated in FIG. 1, the feed electrode 100 is typically placedover a crucible 105 (which may include, consist essentially of, orconsist of, e.g., copper) that may be cooled via flow of coolant (e.g.,water or other heat-exchange fluid) circulating within and/or around thecrucible 105. As shown, the coolant may flow from a cooling inlet 110and out of the crucible 105 via a cooling outlet 115. In variousembodiments, a small charge 120 of the precursor material is positionedat the bottom of the crucible 105, and an electric current (e.g.,hundreds, or even thousands of Amperes of DC current) is applied betweenthe charge 120 and the feed electrode 100. The electrical current, whichmay be applied by a power supply 125, creates an arc 130 between thefeed electrode 100 and the charge 120 within crucible 105, causing thefeed electrode 100 to melt, forming a billet having the shape of theinterior of the crucible 105 (e.g., round and at least partiallycylindrical). A vacuum or other inert atmosphere (e.g., nitrogen gas,argon gas, or other inert gas) may be present within and/or around thecrucible 105, and various volatile impurities within the feed electrode100 may escape into that ambient during the arc melting. The resultingbillet may even be subjected to arc melting one or more additional timesin order to refine the billet material and further reduce theconcentration of various volatile impurities.

After the arc-melting process, the resulting billet is crafted into wireby one or more mechanical deformation processes. For example, the billetmay be hot worked (e.g., extruded, rolled, forged, pilgered, etc.) toform a rod having a diameter smaller than that of the initial billet.The billet and/or the rod may be further densified by pressing, e.g.,cold isostatic pressing or hot isostatic pressing. The rod may then beformed into a wire having the final desired diameter by, e.g., one ormore of drawing, swaging, pilgering, extrusion, etc. (In variousembodiments, the immediate product of the arc-melting process, i.e., thebillet, may be formed into a wire directly, rather than being formedinto a rod therebetween.) In an exemplary embodiment depicted in FIG. 2,the rod 200 is formed into wire 210 via drawing through one or moredrawing dies 220 until the diameter of the wire 210 is reduced to thedesired dimension. In various embodiments, the drawing is supplementedwith or replaced by one or more other mechanical deformation processesthat reduce the diameter (or other lateral dimension) of the rod 200,e.g., pilgering, rolling, swaging, extrusion, etc. The rod 200 and/orwire 210 may be annealed during and/or after diameter reduction (e.g.,drawing). The billet, rod, and/or wire may be heat treated during and/orafter diameter reduction. For example, the billet, rod, and/or wire maybe sintered at a temperature greater than 900° C.

Once wire 210 including, consisting essentially of, or consisting of oneor refractory metals (e.g., molybdenum) is fabricated in accordance withembodiments of the invention, the wire 210 may be utilized to fabricatea three-dimensional part with an additive manufacturing assembly 300.For example, as shown in FIG. 3, the wire 210 may be incrementally fed,using a wire feeder 310, into the path of a high-energy source 320(e.g., an electron beam or a laser beam emitted by a laser orelectron-beam source 330), which melts the tip of the wire 230 to form asmall molten pool (or “bead” or “puddle”) 340. The entire assembly 300may be disposed within a vacuum chamber to prevent or substantiallyreduce contamination from the ambient environment.

Relative movement between a substrate 350 (which may be, as shown,disposed on a platform 360) supporting the deposit and the wire/gunassembly results in the part being fabricated in a layer-by-layerfashion. Such relative motion results in the continuous formation of alayer 370 of the three-dimensional object from continuous formation ofmolten pool 340 at the tip of the wire 230. As shown in FIG. 3, all or aportion of layer 370 may be formed over one or more previously formedlayers 380. The relative movement (i.e., movement of the platform 360,the wire/gun assembly, or both) may be controlled by a computer-basedcontroller 380 based on electronically stored representations of thepart to be fabricated. For example, the two-dimensional layers tracedout by the melting wire may be extracted from a stored three-dimensionalrepresentation of the final part stored in a memory 390.

The computer-based control system (or “controller”) 380 in accordancewith embodiments of the present invention may include or consistessentially of a general-purpose computing device in the form of acomputer including a processing unit (or “computer processor”) 392, thesystem memory 390, and a system bus 394 that couples various systemcomponents including the system memory 390 to the processing unit 392.Computers typically include a variety of computer-readable media thatcan form part of the system memory 390 and be read by the processingunit 392. By way of example, and not limitation, computer readable mediamay include computer storage media and/or communication media. Thesystem memory 390 may include computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) andrandom access memory (RAM). A basic input/output system (BIOS),containing the basic routines that help to transfer information betweenelements, such as during start-up, is typically stored in ROM. RAMtypically contains data and/or program modules that are immediatelyaccessible to and/or presently being operated on by processing unit 392.The data or program modules may include an operating system, applicationprograms, other program modules, and program data. The operating systemmay be or include a variety of operating systems such as MicrosoftWINDOWS operating system, the Unix operating system, the Linux operatingsystem, the Xenix operating system, the IBM AIX operating system, theHewlett Packard UX operating system, the Novell NETWARE operatingsystem, the Sun Microsystems SOLARIS operating system, the OS/2operating system, the BeOS operating system, the MACINTOSH operatingsystem, the APACHE operating system, an OPENSTEP operating system oranother operating system of platform.

Any suitable programming language may be used to implement without undueexperimentation the functions described herein. Illustratively, theprogramming language used may include assembly language, Ada, APL,Basic, C, C++, C*, COBOL, dBase, Forth, FORTRAN, Java, Modula-2, Pascal,Prolog, Python, REXX, and/or JavaScript for example. Further, it is notnecessary that a single type of instruction or programming language beutilized in conjunction with the operation of systems and techniques ofthe invention. Rather, any number of different programming languages maybe utilized as is necessary or desirable.

The computing environment may also include other removable/nonremovable,volatile/nonvolatile computer storage media. For example, a hard diskdrive may read or write to nonremovable, nonvolatile magnetic media. Amagnetic disk drive may read from or writes to a removable, nonvolatilemagnetic disk, and an optical disk drive may read from or write to aremovable, nonvolatile optical disk such as a CD-ROM or other opticalmedia. Other removable/nonremovable, volatile/nonvolatile computerstorage media that can be used in the exemplary operating environmentinclude, but are not limited to, magnetic tape cassettes, flash memorycards, digital versatile disks, digital video tape, solid state RAM,solid state ROM, and the like. The storage media are typically connectedto the system bus through a removable or non-removable memory interface.

The processing unit 392 that executes commands and instructions may be ageneral-purpose computer processor, but may utilize any of a widevariety of other technologies including special-purpose hardware, amicrocomputer, mini-computer, mainframe computer, programmedmicro-processor, micro-controller, peripheral integrated circuitelement, a CSIC (Customer Specific Integrated Circuit), ASIC(Application Specific Integrated Circuit), a logic circuit, a digitalsignal processor, a programmable logic device such as an FPGA (FieldProgrammable Gate Array), PLD (Programmable Logic Device), PLA(Programmable Logic Array), RFID processor, smart chip, or any otherdevice or arrangement of devices that is capable of implementing thesteps of the processes of embodiments of the invention.

Advantageously, wires in accordance with embodiments of the inventioncontain reduced or minimal amounts (if any) of volatile elements such asO, Na, Mg, P, S, K, Ca, and Sb, and therefore the wire 210 melts duringadditive manufacturing with little if any sparking and withoutintroducing porosity, cracks, or other defects into the printed part.After the additive manufacturing process is complete, the part may beremoved from the platform and subjected to final machining and/orpolishing.

Example 1

A Mo wire (wire A) having an outer diameter of 0.062 inches wasfabricated in accordance with embodiments of the present invention.Specifically, wire A was produced by (1) compaction of Mo powder havingpurity of 99.95% into a rod, (2) sintering of the rod to form a feedelectrode, (3) arc melting of the feed electrode under vacuum within awater-cooled copper crucible to form a billet, and (4) hot working ofthe billet in order to reduce its diameter. For comparison, a control Mowire (wire B) having an outer diameter of 0.062 inches was fabricatedvia conventional powder-metallurgy techniques. Specifically, wire B wasproduced by (1) compaction of Mo powder having purity of 99.95% into abillet, (2) sintering the billet in a hydrogen atmosphere to a densityof at least 93%, and (3) hot working of the billet in order to reduceits diameter. Detailed compositional information for various impurityspecies in both wires was obtained via glow discharge mass spectrometry(GDMS) and is presented in Table 1.

TABLE 1 Composition in Composition in Element Wire A (ppm) Wire B (ppm)Na 0.1 21 Mg 0.04 5.8 Si 5 34 P 0.97 3.6 K 0.06 2.4 Ca 0.53 21 Sb 0.6718 O 18 28

As shown in Table 1, wire A contained significantly less of severalvolatile impurities than wire B.

Example 2

Wires A and B from Example 1 were utilized in an exemplary additivemanufacturing process to fabricate a three-dimensional Mo part. Eachwire was heated to melting during the fabrication process via anelectron beam having an average power of 35 kV at 110 mA (pulsed). Thewire feed speed into the electron beam was approximately 30 in/min, andthe relative travel speed between the wire and the fabrication platformwas 10 in/min. The deposition rate was approximately 0.91 kg/hr.

During fabrication using wire A, the deposition was smooth andsubstantially free of sparking, blistering, and splattering. FIG. 4 isan image of the molten bead 400 forming at the tip of wire A during theadditive manufacturing process. FIG. 5 is an image of the resulting part500 manufactured utilizing wire A. As shown, the part 500 is free ofvisible cracks or other imperfections, and the fabrication platform isfree of visible splatter or other debris. As shown in FIG. 6, the part500 could be machined and/or polished, in to remove any roughnessresulting from the layer-by-layer fabrication process, without crackingor other damage.

During fabrication using wire B, the deposition was plagued by sparkingand blistering. FIG. 7 depicts the molten bead 700 forming at the tip ofwire B during the additive manufacturing process. As shown, wire Bpossessed a large number of pores or inclusions 710 due to, e.g., thehigher concentration of volatile impurities within wire B. In addition,visible sparks 720 from wire B resulted during the melting andfabrication process. FIGS. 8A and 8B are images of the three-dimensionalpart 800 fabricated utilizing wire B. As shown, part 800 had visiblecracking in its walls, and there was visible splattering of the wirematerial on the fabrication platform and on the part 800 itself.Attempted machining of part 800 was unsuccessful, and part 800 wasunsatisfactory for use as a crucible, in stark contrast to part 500.

The densities of the finished parts 500, 800 were measured, and theresults are presented in Table 2 below.

TABLE 2 Part/Location Density % of Theoretical within part (g/cc)Density 500/Top of wall 10.13 99.1 500/Bottom of wall 10.14 99.2 800/Topof wall 9.73 95.2 800/Middle of wall 9.81 96.0 800/Bottom of wall 9.7595.4

As shown, the part 500 fabricated using wire A had a density much higherthan that of the part 800 fabricated using wire B. In addition,compositional analysis of the fabricated parts 500, 800 was performed byGDMS, and the results are shown in Table 3 below.

TABLE 3 Composition in Composition in Element Part 500 (ppm) Part 800(ppm) Na 0.01 2.4 Mg 0.08 0.21 Si 12 31 P 0.27 1 K 0.07 1.8 Ca 0.06 1.2Sb 0.09 1.3 O <5 (less than 5.5 detection limit)

As shown in Table 3, the concentrations of most of the impurity elementsdecreased during the fabrication process, presumably due to melting ofthe wire and volatilization of the impurities. However, the part 500fabricated utilizing wire A had concentrations of these impurities thatwere much lower than those in the part 800 fabricated utilizing wire B.In addition, even though the amounts of these impurity elements withinthe part 800 fabricated utilizing wire B tended to be lower than theimpurity levels within wire B itself, the part 800 fabricated utilizingwire B had unacceptable morphology and density, and was accompanied bysplatter and sparking during fabrication, as shown in FIGS. 8A and 8Band discussed above.

The terms and expressions employed herein are used as terms andexpressions of description and not of limitation, and there is nointention, in the use of such terms and expressions, of excluding anyequivalents of the features shown and described or portions thereof. Inaddition, having described certain embodiments of the invention, it willbe apparent to those of ordinary skill in the art that other embodimentsincorporating the concepts disclosed herein may be used withoutdeparting from the spirit and scope of the invention. Accordingly, thedescribed embodiments are to be considered in all respects as onlyillustrative and not restrictive.

What is claimed is: 1.-14. (canceled)
 15. A three-dimensional metallicpart manufactured by additive manufacturing using a metallic feedstockmaterial, the part (i) comprising a plurality of layers of one or moreof molybdenum, niobium, rhenium, or tungsten, (ii) being free of gapsbetween successive layers, and (iii) being free of cracks, wherein adensity of the part is no less than 97% of a theoretical density, andwherein a concentration within the part of at least one of sodium,silicon, calcium, antimony, magnesium, phosphorous, sulfur, or potassiumis less than 20 ppm by weight and at least 0.001 ppm by weight.
 16. Thepart of claim 15, wherein the concentration within the part of each ofsodium, silicon, calcium, antimony, magnesium, phosphorous, sulfur, andpotassium is less than 20 ppm by weight and at least 0.001 ppm byweight.
 17. The part of claim 15, wherein the concentration within thepart of each of sodium, silicon, calcium, antimony, magnesium,phosphorous, sulfur, and potassium is less than 10 ppm by weight and atleast 0.001 ppm by weight.
 18. The part of claim 15, wherein theconcentration within the part of each of sodium, silicon, calcium,antimony, magnesium, phosphorous, sulfur, and potassium is less than 5ppm by weight and at least 0.001 ppm by weight.
 19. The part of claim15, wherein the concentration within the part of at least one of sodium,silicon, calcium, antimony, magnesium, phosphorous, sulfur, or potassiumis less than 10 ppm by weight and at least 0.001 ppm by weight.
 20. Thepart of claim 15, wherein the concentration within the part of at leastone of sodium, silicon, calcium, antimony, magnesium, phosphorous,sulfur, or potassium is less than 5 ppm by weight and at least 0.001 ppmby weight.
 21. The part of claim 15, wherein a concentration within thepart of oxygen is less than 20 ppm by weight and at least 0.001 ppm byweight.
 22. The part of claim 15, wherein a concentration within thepart of oxygen is less than 10 ppm by weight and at least 0.001 ppm byweight.
 23. The part of claim 15, wherein a concentration within thepart of oxygen is less than 5 ppm by weight and at least 0.001 ppm byweight.
 24. The part of claim 15, wherein a concentration within thepart of oxygen is less than 3 ppm by weight and at least 0.001 ppm byweight.
 25. The part of claim 15, wherein the feedstock materialcomprises wire.
 26. The part of claim 15, wherein the feedstock materialis arc-melted.
 27. The part of claim 15, wherein the feedstock materialis fabricated by a process comprising arc-melting metallic powder. 28.The part of claim 15, wherein the density of the part is no less than99% of the theoretical density.
 29. A three-dimensional partmanufactured by additive manufacturing using a feedstock materialcomprising a metallic material comprising at least one of niobium,tantalum, rhenium, or tungsten, the part (i) comprising a plurality oflayers each comprising solidified metallic material, (ii) being free ofgaps between successive layers, and (iii) being free of cracks, whereina density of the part is no less than 97% of a theoretical density ofthe metallic material, and wherein a concentration within the part of atleast one of sodium, silicon, calcium, antimony, or potassium is lessthan 20 ppm by weight and at least 0.001 ppm by weight.
 30. The part ofclaim 29, wherein the concentration within the part of at least one ofsodium, silicon, calcium, antimony, or potassium is less than 10 ppm byweight and at least 0.001 ppm by weight.
 31. The part of claim 29,wherein the concentration within the part of each of sodium, silicon,calcium, antimony, and potassium is less than 20 ppm by weight and atleast 0.001 ppm by weight.
 33. The part of claim 29, wherein theconcentration within the part of each of sodium, silicon, calcium,antimony, and potassium is less than 10 ppm by weight and at least 0.001ppm by weight.
 34. The part of claim 29, wherein a concentration withinthe part of oxygen is less than 20 ppm by weight and at least 0.001 ppmby weight.